Outgassing technique

ABSTRACT

An outgassing technique which comprises providing a chemical liner for a casing or container which will decompose into a gas with sufficient pressure to rupture the casing when the container is subjected to a high heat source. This allows release of any material within the container.

1451 July 31, 1973 United States Patent 1 1 Pakulak, JR",

[ 1 OUTGASSING TECHNIQUE 3,401,632 9/1968 Gritfith 102 24 R [75]Inventor: Jack Pakulak Jr" China Lake 2,075,969 4 1937 Whlte et al..102/24 R Cahf' FOREIGN PATENTS OR APPLICATIONS [73] Assignee: The UnitedStates of America as 423,040 1/1935 Great Britain.................102/D1G. 8

represented by the Secretary of the Navy, Washington, DC.

Apr. 26, 1971 Primary Examiner-Robert F. Stahl [22] Filed:

Attorney-R. S. Sciascia and R0) Miller 21 Appl. 110.; 137,557

ABSTRACT 102/56, 102/103 F42b l/00, F42b 25/00, F42b 3/00 An outgassingtechnique which comprises providing a g 1 02/103 24 2 90 chemical linerfor a casing or container which will decompose into a gas withsufiicient pressure to rupture the casing when the container issubjected to a high 102/56, 38, DIG. 8, 101

heat source. This allows release of any material within the container.

2,563,265 Parsons........................... 102/103 X 5 Claims, 1Drawing Figure PATENTED JUL 3 1 I II I l I I I I I II I I I II 1 I I IINVENTOR. JACK M. PAKULAK, JR

BY I ROY MILLER ATTORNEY.

1 OUTGASSING TECHNIQUE BACKGROUND OF THE INVENTION The present inventionrelates to an outgassing technique; more specifically, the placing of agas producing chemical liner in a container which when subjected to aheat source creates sufficient pressure to rupture the container.

Various methods for rupturing containers such as warhead casings, bombhousings and other sealed vessels adapted for retaining explosives,pyrotechnics, propellants, pellets, antipersonnel material, etc., areknown. However, means for causing rupture at a predetermined temperaturehas presented a problem. In the ordnance field detonation on the fastcook-off of a warhead or possibly a bomb creates a hazardous situation.Various techniques have been used to achieve the basic result which isto split the casing of the warhead or bomb open and permit the explosivecontained therein to burn unconfined. A gas generating chemicalformulation added to the high explosive has been utilized. The presentinvention provides a method of outgassing whereby the liner inside thecontainer or casing consists of a gas generating chemical and/or binderwhich will decompose into a gas with sufficient pressure to rupture thecasing when the casing is subjected to heat.

DESCRIPTION OF THE DRAWING The single FIGURE shows a container whichuses the outgassing chemical liner in accordance with this invention.

DESCRIPTION OF THE INVENTION The present invention is for an outgassingtechnique or method illustrated in the single FIGURE which comprisescovering the inside walls of container or casing (which can be adaptedto be hermetically sealed) with a chemical mixture to form a linerll ofpredetermined thickness. Liner 11 consists essentially of a gasgenerating chemical compound blended into a compatible binder for easein painting, dipping, or otherwise suitably coating the inside of thedesired container. When the container is subjected to heat, the linerdecomposes into a gas with sufficient pressure to rupture the containerand allow the contents to spill out. In the single FIGURE of the presentinvention a bomb casing 10 is shown loaded with high explosive,designated 12. When the casing breaks the explosive deflagrates andburns in an unconfined condition. Warheads were also lined with thechemical blend, filled with explosive, and heated until the gas pressurecreated by decomposition of the liner ruptured the warhead releasing theexplosive. The common problem to both warhead and bomb devices is thepossibility of a detonation occurring during a gasoline or similar tire.The present invention is primarily concerned with preventing adetonation by creating sufficient excess pressure in the liner to splitopen a given bomb or warhead casing and allow the explosive todeflagrate and burn in an unconfined condition. It should be noted thatnot all explosives just burn when in an unconfined state; some detonateand set off a chain reaction of detonating bombs or warheads stored orstock-piled. This invention postulates that a thick liner with a gasgenerating chemical compound added could increase the time to open thecase by a pressure rupture. Study of the problem indicated that thechemical compound used in such a liner should contain certain basicproperties such as (a) an endothermic decomposition, (b) a high density,(c) ability to decompose completely into a gas having a low molecularweight, (d) decomposition should not start until a predeterminedtemperature and then gas release should be immediate, (e) mole ratio ofgas generated to chemical should be high, and (f) chemical compound mustbe compatible with the explosive or other material to be used.

One liner composition used successfully as a bomb casing liner such asshown in the single FIGURE consisted essentially of a mixture of about10 pounds ammonium oxalate and 1.6 pounds of hot melt; anothercomposition used consisted essentially of about l0 pounds of ammoniumoxalate mixed with 2 pounds of black cavity paint. The cavity paint is abituminous mixture either liquid or semiliquid at room temperature andthe hot melt is a mixture of bitumens which occur in nature such asasphalt. The following Table I gives the results of fast cook-ofiobtained on a bomb containing standard Composition B explosive.

TABLE I. FAST COOK-OFF MK 82 (NO FUSE) A0 ammonium oxalate Notes: I.About 10 pounds of ammonium oxalate mixed with about 1.6 pounds of meltwas used for the liner in the bomb. This bomb may have been defective,the weld had a break present before the test. 2. About 10 pounds ofammonium oxalate mixed with 2 pounds of black cavity paint was used forthe liner in these two bomb tests.

3. Four pounds overpressure at 20 feet.

Other binder materials may be used such as polyurethane andpolybutadiene.

A deflagration is desired and an explosion is tolerated. The mainobjective of this invention is to avoid detonation of explosives in thecontainer. The minimum cook-off reaction time is 5 minutes.

Warheads and bombs contain various high explosives. Composition B isused extensively in bombs. It was developed by the British during theperiod between World Wars I and II and was standardized by the UnitedStates in World War II. It consists of 55.2 percent RDX(cyclotrimethylenetrinitramine), 40 percent TNT (trinitrotoluene), 1.2percent polyisoluctylene, and 0.6 percent wax.

A series of quick cook-off tests have been made with a modern warhead.The work was done to determine the reaction of the warhead whensubjected to an enveloping flame. The enveloping flame for the quickcook- 011' test was produced by burning 450 gallons of aviation gasolinein a shallow-steel pan, which had about gallons of water for leveling.The pan was one foot deep and 9 10 feet wide by 15 feet long, with thepan size depending on the pan used in a particular test. Thethermocouple leads were protected from direct contact with the flame bythe use of insulating material, although this was not always successful.The warhead in each test was suspended from a railroad rail by a chainand lugs about 3 feet above the gasoline. The gasoline was ignitedremotely, using a flare for each test. The flames usually completelyenveloped the warhead and i mateiiise'coomow DATA ON WARHEAD Thickness(mils) Test results 20 (est.) Detonation; 3 minutes, seconds. 20 (estDetonation (Note #1); 6 minutes, 20 seconds.

Explosive Booster Liner material PBXN-lOl Comr'giosition B Yes"... Redcavity paint Yes Black cavity paint No Black cavity paint One procedurefor lining a bomb casing comprises pouring the mixture into the casingand then pouring 20 plus inch bead. Case opened, defiagration; 4minutes, 25 seconds.

with A0 Yes .do -l00 Case opened, deflagration; 5 minutes, 0 seconds.

Yes. do -100 End opened, deflagration; 5 minutes, seconds. No Hot melt.100-175 Case opened, deflagration; 2 minutes, seconds. Do No ..do100-200 Case opened, deflagration; 2 minutes, 0 seconds.

Nora-A0 =Ammonium oxalate; No. 1 reaction started in approximately 2minutes rupturing both .end plates.

Several chemical compounds can be used due to their decompositionmechanism. Ammonium oxalate has been used and tested successfullybecause of its availability. The overall mechanism is listed below forseveral compounds mixed with black cavity paint or a hot melt consistingessentially of bituminous which occur in nature.

1. Ammonium oxalate (A0, 230 250 C.):

NmooccooNm-mosmo NCCN 2. Oxalic acid (150 C.):

Hooccoon-" co, co 14,0

3. Oxamide (230 250 C.):

Nl-LOCCONih Q 11,0 NCCN 4. Urea oxalate (178 234 C.):

CO(NH ),C,I-I O 'H,O 2CO, NH; H,O CO

Urea oxalate is very promising since itsg'as'pre'ssnre is not basedsolely on the amount of water produced.

Other outgassing chemicals which cover the a pprox i mate range of 103375 C. which may be used include ammonium formate, S-amino-lH-tetrazole,oratic acid, semi-oxamazide and l-formyl-3- thiosemicarbazide (whichexhibit endothermic decomposition) and nitroguanidine, guanidinenitrate, oxalohydroxamic acid, ammonium nitrate and ammonium perchlorate(which exothermically decompose). For higher temperature (200 l,000 C.)outgassing chemicals the following may be used depending upon theircompatibility with the explosive and liner binder:

oxalates: sodium, potassium, magnesium, calcium,

aluminum and titanium;

carbonates: lithium, sodium, potassium, magnesium,

calcium;

formates: magnesium, aluminum and sodium;

acetates: sodium, potassium, magnesium and calcium; and iodic acid.

I The method comprises coating or lining the inside of a warhead, bombcasing or other desired container with an outgassing mixture consistingessentially of a gas generating chemical compound blended into a binderwhich is compatible with both the compound and the material whichsubstantially fills the container, such as explosive, propellant orpyrotechnic. The coating or out tiliiintuiefriisgives'a'smobmurraee suchas obtained in lining small cans.

Another means for lining a container which is well known to the artcomprises pouring a predetermined amountof the gas producing mixtureinto the preselected container, then rolling the container until theinterior walls are evenly coated.

Lining bomb and warhead casings as described herein will alleviate thehazards of fire on the flight deck of an aircraft carrier caused byexisting airborne weapons and stock piles. This invention will aid indelaying and in minimizing the damaging effects of cookoff.

What is claimed is:

l. A method for preventing a sealed vessel which contains an explosivefrom detonating on fast cook off of said explosive, said methodcomprising placing a liner between the explosive and the interior wallsof the vessel which, when exposed to a temperature of a predeterminedmagnitude, will produce gases; heating the vessel to decompose theliner; and rupturing the vessel by gases produced by the decomposing ofsaid liner to permit the explosive to burn without exploding.

2. The method in accordance with claim 1 wherein said liner comprises abinder consisting essentially of bitumens which occur in nature and achemical compound which will decompose into gases when subjected to heatfrom a source outside said vessel.

3. The method in accordance to claim 2 wherein said chemical compoundexhibits endothermic decomposition into gases and is selected from thegroup consisting of ammonium oxalate, oxalic acid, oxamide, ureaoxalate, ammonium formate, S-amino-lI-i-tetrazole; orotic acid,semioxamazide, and l -formyl-3- thiosemicarbazide.

4. The method in accordance with claim 2 wherein said chemical compoundexhibits exothermic decomposition into gases and is selected from thegroup consisting of nitroguanidine, guanidine nitrate, oxalhydroxamicacid, ammonium nitrate and ammunium perchlorate.

5. The method in accordance with claim 2 wherein said chemical compounddecomposes into gases at'a temperature between 200 and l,000C and isselected from the group consisting of the oxalates of sodium, potassium,magnesium, calcium, aluminum, and titanium, the carbonates of lithiumsodium, potassium, magnesium, and calcium, the formates of magnesium,aluminum, and sodium, the acetates of sodium, potassium,

magnesium, and calcium and iodic acid.

. III I t i

1. A method for preventing a sealed vessel which contains an explosive from detonating on fast cook off of said explosive, said method comprising placing a liner between the explosive and the interior walls of the vessel which, when exposed to a temperature of a predetermined magnitude, will produce gases; heating the vessel to decompose the liner; and rupturing the vessel by gases produced by the decomposing of said liner to permit the explosive to burn without exploding.
 2. The method in accordance with claim 1 wherein said liner comprises a binder consisting essentially of bitumens which occur in nature and a chemical compound which will decompose into gases when subjected to heat from a sourcE outside said vessel.
 3. The method in accordance to claim 2 wherein said chemical compound exhibits endothermic decomposition into gases and is selected from the group consisting of ammonium oxalate, oxalic acid, oxamide, urea oxalate, ammonium formate, 5-amino-1H-tetrazole; orotic acid, semioxamazide, and 1-formyl-3-thiosemicarbazide.
 4. The method in accordance with claim 2 wherein said chemical compound exhibits exothermic decomposition into gases and is selected from the group consisting of nitroguanidine, guanidine nitrate, oxalhydroxamic acid, ammonium nitrate and ammunium perchlorate.
 5. The method in accordance with claim 2 wherein said chemical compound decomposes into gases at a temperature between 200* and 1,000*C and is selected from the group consisting of the oxalates of sodium, potassium, magnesium, calcium, aluminum, and titanium, the carbonates of lithium sodium, potassium, magnesium, and calcium, the formates of magnesium, aluminum, and sodium, the acetates of sodium, potassium, magnesium, and calcium and iodic acid. 